In an internal combustion engine of a motor vehicle, a camshaft that is in driven connection with a crankshaft is typically used for actuating the gas exchange valves. Here it has proven advantageous to be able to change the opening and closing times of the gas exchange valves while the internal combustion engine is running. By adjusting the opening and closing times, for example, as a function of the current rotational speed, in particular, the fuel consumption can be reduced, the exhaust gas behavior can be positively influenced, and the engine efficiency can be increased.
The variability of the gas exchange valve control times is usually achieved through a relative change of the phase position of the camshaft relative to the crankshaft. For this purpose, typically a so-called camshaft adjuster is integrated into the drive train by means of which the torque is transferred from the crankshaft to the camshaft. The mounting of modern camshaft adjusters is located, for example, on the drive-side end of the camshaft, on an intermediate shaft, on a non-rotating component, or on the crankshaft.
The crankshaft adjuster is here constructed such that, during the operation, the phase position between the crankshaft and camshaft can be reliably maintained and if necessary the camshaft can be rotated in a certain angle range relative to the crankshaft. For this purpose, the camshaft adjuster is formed essentially with at least two pressure chambers acting against each other. Through targeted connection of the pressure chambers with a pressurized medium pump or with a pressurized medium tank, the phase of the camshaft can be adjusted or maintained relative to the crankshaft.
The pressurized medium supply to the pressure chambers and the pressurized medium discharge from the pressure chambers is usually controlled by means of a control valve, usually in the form of a multiple-path gate valve. This typically comprises, as essential components, a valve housing and a control piston that is held in a housing hollow space so that it can move in the axial direction and that is actuated by an actuator, typically an electromagnet. The control valve also has, in particular, a pressurized medium connection, a discharge connection and work connections by means of which the pressurized medium can be injected into a pressure chamber or discharged out from a pressure chamber. Depending on the position of the control piston, for example, one of the pressure chambers is connected to the supply connection via one of the work connections and is filled with pressurized medium. At the same time, the opposing pressure chamber communicates via the work connection allocated to it with the discharge connection on the control valve and is in this way emptied.
In one common construction, such a control valve is constructed, for example, as a so-called central valve that is inserted into a central hole of the camshaft adjuster and is screwed to the camshaft.
A control valve of the type noted above is disclosed, for example, in DE 10 2008 004 591 A1. The illustrated control valve for controlling pressurized medium flows of a camshaft adjuster of an internal combustion engine comprises an essentially hollow cylindrical valve housing in which a hollow pressurized medium guide insert is inserted. Within the pressurized medium guide insert, there is a control sleeve in which a guided control piston sits that can move in the axial direction. In the valve housing, a radial hole is formed that is used as a pressurized medium supply and is connected to a pressurized medium pump for feeding pressurized medium. A hydraulically releasable non-return valve is also used in the region of the pressurized medium supply.